1. Field of the Invention
The present invention relates to an apparatus and a method for applying a conductive paste, for forming electrodes, onto an electronic component, especially a (micro) chip device, and more particularly to an apparatus and a method for applying a conductive paste onto an electronic component to allow the conductive paste to be precisely applied onto the electronic component and to precisely adjust the amount of the applied conductive paste.
2. Description of the Related Art
In a manufacturing process of an electronic component, for example, a micro chip device, such as a multi layer ceramic capacitor (MLCC), a method for forming external electrodes on the chip device by applying a conductive paste for the external electrodes onto the chip device and baking the conductive paste has been widely used.
However, in case that the conductive paste for forming external electrodes is applied onto the electronic component, such as the micro chip device, as the chip device has been recently miniaturized, the precision in applying the conductive paste onto the chip device becomes an issue.
For example, FIG. 1 illustrates a conventional chip device, and FIG. 2 illustrates a conventional highly dense chip device.
The highly dense chip device 110 of FIG. 2 is an array type, and thus a plurality of external electrodes 112 are formed on one chip device 110. That is, a plurality of chip units is integrated into one highly dense chip device 110.
In order to satisfy the mounting requirement of the chip device on a substrate, the amount of the applied conductive paste has been increased, the performance of the chip device has been improved, and further, the chip device has been developed to a small size. There is a clear distinction between the highly dense chip device 110 and the general chip device 100 of FIG. 1. For example, the highly dense chip device 110 of FIG. 2 comprises four circuits (not shown), and eight micro (external) electrodes 112, each of which is formed at both sides of the corresponding one of the circuits.
However, the general chip device 100 of FIG. 1, which is not integrated, comprises one circuit, and two (external) electrodes 102, each of which is formed at both sides of the circuit.
One of important problems to be solved for achieving the highly dense integration of the chip device is how to precisely form electrodes on the micro chip device, and the precise formation of the electrodes depends on the precision in applying a conductive paste onto the micro chip device.
For example, conventional conductive paste applying methods can be used to apply a conductive paste onto a micro chip device having a size of 2 mm×1.2 mm (hereinafter, referred to as a “2012 device”), which has been mainly used, so as to maintain the precision in applying the conductive paste. However, the above method cannot be substantially used to precisely apply a conductive paste onto a micro chip device having a smaller size of 1.6 mm×0.8 mm (hereinafter, referred to as a “1608 device”) and a micro chip device having a smaller size of 1.0 mm×0.5 mm (hereinafter, referred to as a “1005 device”), thus generating problems in manufacturing micro chip devices.
FIGS. 3 and 4 illustrate conventional methods for applying a conductive paste onto a chip device.
FIG. 3 illustrates a method for applying (transferring) a conductive paste using wheels. In this method, a conductive paste is applied onto an electronic component using wheels 120 made of rubber or urethane.
As shown in FIG. 3, an electronic component, for example, a chip device 110, is mounted on a carrier tape (not shown), and the wheels 120, each of which is provided with grooves 124 filled with a conductive paste 122, continuously contact the chip device 110 while rotating. Thereby, the conductive paste 122 is applied onto the chip device 110 and it is possible to achieve mass production of the chip device 110.
Further, FIG. 4 illustrates a method for applying a conductive paste using a plate.
In this method of FIG. 4, a conductive paste 132 is applied onto the micro chip device 110 using a flat plate 130. The flat plate 130 is made of rubber or urethane, and is provided with grooves 134 filled with the conductive paste 132.
The above method apply (transfer) the conductive paste 132 simultaneously onto several hundreds of devices by increasing the size of the flat plate 130 and the size of a carrier plate for fixing the components, for example, a jig.
However, the above conventional applying methods generate several problems. For example, as shown in FIGS. 3 and 4, the wheels 120 and the flat plate 130, which are made of rubber or urethane, may be easily damaged by pressure applied thereto when the conductive paste is applied onto the electronic component. Thus, it is difficult to precisely apply the conductive paste onto the electronic component.
Since the wheels and the flat plate have a limitation in applying the conductive paste thereonto, the conventional applying methods cannot be used to manufacture micro chip devices having a size less than that of the 1608 device.
The amount of the applied conductive paste is limited due to the surface tension of rubber or urethane. For example, only approximately 50% of the total amount of the conductive paste filling the grooves of the wheels or the flat plate is substantially applied onto the chip device, thus causing problems, such as cleaning of remaining paste, and in a serious case, the replacement of the wheels or the flat plate with a new one.
The wheels and the flat plate, which are made of rubber or urethane, are easily abraded by the pressure, thus having a shortened life span.
In order to solve the above problems, Japanese Patent Laid-open Publication No. 1997-148723 discloses a solder ball transfer jig. The solder ball transfer jig comprises a transfer mask and a plate. The transfer mask is provided with discs each having a recess on its top surface is carrying a solder ball to be supplied to each of pads of a substrate, and holes each having an elastic member inserted thereinto. The plate is provided with projections inserted into the holes of the transfer mask for pushing the solder balls against the pads of the substrate, and moves below the transfer mask.
Since a conductive paste does not fill the transfer mask, the above transfer jig cannot use the applying method, in which the transfer jig is filled with the conductive paste. Further, the transfer jig uses the discs and the elastic members, which are separately prepared, thus having a complicated structure.